1. Field of the Invention
This invention generally relates to electronic communication receiver circuitry and, more particularly to a low-power two-stage automatic gain control (AGC) that incorporates a frequency equalization function.
2. Description of the Related Art
Two primary components of a modern communications receiver front end are an AGC and an equalizer. Since the input signal strength is both unknown and subject to change, an AGC is required to amplify the input signal to a predetermined constant signal level for subsequent processing. An equalizer is typically required to compensate for signal bandpass degradation that may occur in the transmission channel.
FIG. 1 is a schematic block diagram of an exemplary equalizer (prior art). A received signal can be multiplexed through either a high pass or low pass signal path to compensate for signal bandpass degradation.
Generally, AGC is an adaptive system where the average output signal level is fed back to adjust the gain to a predetermined power, for a relatively large dynamic range of input signal levels.
High speed receiver front ends impose strict constraints on the quality of the analog front ends. Power, noise, bandwidth, and signal integrity all have to be optimized at the same time. To this end, a high-performance front stage is a critical component to these systems. Conventional front ends are relatively power hungry in performance of these goals.
It would be advantageous if a combination AGC/equalizer circuit existed that provided a high level of performance, while minimizing power consumption.